1. Field of the Invention
The present invention relates to a vehicle windshield wiper, and more particularly to a windshield wiper having a variable wiping stroke.
2. Description of the Prior Art
A stroke adjustable vehicle windshield wiper has been known in the art. An example of the prior art structure is shown in FIG. 31. A wiper arm 106 carrying a wiper blade is mounted at one end on a vehicle body by means of a pin 105 for a reciprocating swinging movement and securely attached to one end of a lever 107 which is connected at the other end with one end of an actuating rod 104. A wiper driving motor is provided with an output shaft which is connected with an eccentric shaft 101. A crank lever 103 is provided to connect the other end of the actuating rod 104 with the eccentric shaft 101. The crank lever 103 is connected with the eccentric shaft 101 through a crankpin 102 which is disengageably secured to the eccentric shaft 101.
In the structure disclosed in FIG. 31, the wiper driving motor is operated to rotate the eccentric shaft 101 with the crankpin 102 engaged with the eccentric shaft 101 to securely connect the crank lever 103 to the eccentric shaft 101. The rotation of the eccentric shaft 101 causes the end of the crank lever 103 which is connected to the actuating rod 104 to rotate along a path which is shown by a broken line in FIG. 31. Thus, the rod 104 is moved to reciprocate in a substantially axial direction causing the lever 107 and the wiper arm 106 to swing about the pin 105. When it is desired to place the wiper blade in a park position, the crank pin 102 is disengaged from the eccentric shaft 101 and moved to the position shown by 102a in FIG. 31 to be secured to the shaft 101 again at this position. The end of the lever 103 which is connected to the rod 104 is then shifted to the position shown by A in FIG. 31 so that the wiper arm 106 is placed at a park position beyond the wiping stroke range.
It should however be noted that the prior art structure discussed above can provide the wiper park position outside the wiper stroke but it cannot change the wiping stroke during operation of the wiper. When the vehicle windshield wiper is being operated while the vehicle is running, the wiper blade is subjected to a wind force which tends to move the wiper blade beyond a desired wiping stroke. Such wind force sometimes cause the wiper blade to hit the front pillar of the vehicle or in a worst case to move beyond the front pillar. It should further be noted that the wind force on the wiper blade is transmitted through the actuating mechanism to the wiper motor so that the wiper driving structure must be such that it can overcome the wind force acting on the wiper blade. For this reason, a bulky worm gear mechanism has been required.